Answer : 4. "member nations"
Explanation :

The United Nations is primarily funded by its member nations. Member states contribute funds to support the regular budget of the United Nations, which covers essential expenses for the organization's operations. Assessments for the regular budget are based on a country's capacity to pay, taking into account its relative wealth and income. Additionally, the UN may receive voluntary contributions for specific programs or initiatives from member nations and other entities. Therefore, the correct answer is:

(D) Member Nations